function wpcode_snippet_replace_howdy( $wp_admin_bar ) {

	// Edit the line below to set what you want the admin bar to display intead of "Howdy,".

	$new_howdy = 'Welcome,';

	$my_account = $wp_admin_bar->get_node( 'my-account' );

	if ( ! isset( $my_account->title ) ) {

		return;

	}

	$wp_admin_bar->add_node(

		array(

			'id'    => 'my-account',

			'title' => str_replace( 'Howdy,', $new_howdy, $my_account->title ),

		)

	);

}

add_filter( 'admin_bar_menu', 'wpcode_snippet_replace_howdy', 9999 );